i hear the cardigans aren't as smart and not as good natured. they are actually a seperate breed, they have a different genetic line.
i had a pembroke for a long time (died 5-6 years ago) and it was a stellar dog. you get all the advantages of a smallish dog (less food, poop, smaller beds, easier to take in the car, etc) with none of the disadvantages that most little dogs have (overbred, stupid, yappy, fragile, genetic problems). Basically you're getting a medium sized dog with short legs. Their bark is low pitched and easy on the ears.
I can't tell you what a great dog ours was. Not only did it learn multiple words for things like "dinner," "ball," or "walk," it learned the spellings of those words too. We had to refer to things as "ovoid recreational object" or "perambulate" so she wouldn't understand us. She knew everyone in the families' name and would run to them if you asked them where that person was. She would try to protect us from fire, even candles or fireplaces. etc, etc.
Things to watch out for/ warnings: These dogs shed. A lot. Their hair comes out in tufts, like yak hair. They have two big sheds, one in the spring and one in fall, and in between they shed a little bit. You just need to brush them regularly (every few days, like while you watch TV) and you'll be ok. Also, these dogs have a herding instinct (they herd cattle by trade). They will herd your kids around by nipping at their heels. You will need to break them of this, which means you will probably need some obidiance school if you're not experienced in dog training. But they will learn quickly that nipping and herding are not acceptable and you won't have problems after that. Lastly, these are long dogs with a medium build and short legs, and that means you should discourage them from making big jumps, especially in/out of the car, because they can and will develop strained backs. So just lift them in and out of the car and don't play fetch up and down the staircase, and they'll be fine.
Good luck!